DESCRIPTION: (Applicant's Abstract) A growing body of work suggests that retinal cells carry positional markers. These markers serve to distinguish cells in different regions of the retina from one another, and they appear to be important in mediating specific cell-cell interactions. Although there is strong evidence for functional differences in the cells on the nasal and temporal sides of the developing retina, there is limited knowledge of the molecular diversity that underlies these differences. The goal of this project is to identify molecules asymmetrically expressed in the nasal-temporal axis of the developing retina and to determine the function of these molecules. The project is divided into four specific aims.First, TRAP, a molecule expressed by most ganglion cells on the temporal side of the retina and by few ganglion cells on the nasal side, will be characterized in more detail. This will involve cloning the gene for TRAP from a cDNA library, sequencing the gene, and developing antibodies to the protein for use in analyzing the function of TRAP. Second, three complementary approaches will be used to identify other molecules expressed asymmetrically between the nasal and temporal sides of the developing retina. These approaches include the use of monoclonal antibodies, cDNA cloning by subtractive hybridization, and lectin blots. As molecules are discovered, they will be characterized as described for TRAP. Third, anatomical differences between the nasal and temporal sides of the retina will be identified.This information will be used to develop in vivo assays to study the function of side-specific molecules and will allow specific patterns of axon growth to be correlated with the distribution of asymmetrically distributed molecules. Fourth, the function of molecules asymmetrically expressed in the developing retina will be examined. This will involve perturbing the function of these molecules with antibodies in vivo and in vitro. Preliminary studies will also evaluate techniques for introducing genes to alter the expression of specific molecules.